Delivery of therapeutic agents to the interior of vessels is a growing field of interest. For example, adverse remodeling of the myocardium and associated long-term damage may be reduced or prevented by delivering mesenchymal stem cells after stent reperfusion following a myocardial infarction. This and other treatments are performed by positioning a standard angioplasty balloon near the treatment site. A balloon may be placed, for example, at the site of previous stenting. The balloon is inflated at or near the desired treatment site, and inflated to a pressure sufficient to seal the vessel and prevent blood flow. The guide-wire lumen of the balloon is then used to deliver a therapeutic agent.
Methods utilizing standard angioplasty and similar balloons and balloon catheters may be undesirable for several reasons. In general, the devices are neither designed for nor approved for such use. There is thus some uncertainty in the safety and effectiveness of such procedures. For example, the guide-wire lumens typically used with such balloons are relatively small, often about 0.015″ or less. Some therapeutic agents, such as slurries of mesenchymal stem cells or other cells, may be relatively viscous and heterogeneous suspensions. When forced through the narrow guide-wire lumen, the lumen may become clogged. Forcing cell slurries through the narrow lumen may also result in high shear forces on the cells, rendering them inactive. Additionally, during occlusion of the vessel, the balloons can exert high radial pressure on the vessel. This pressure can result in trauma or damage to the vessel, causing well-known complications such as restenosis.
Stents are often utilized in place of or in conjunction with balloons in order to avoid restenosis and other similar conditions. As discussed above, use of a standard balloon catheter may be undesirable for delivery of desired or necessary therapeutic agents to a treatment site, such as a previously-positioned stent. However, treatments utilizing a bolus injection of therapeutic agent delivered at high pressure may still be desirable or necessary.